Vegetable Staticks. 89 



the tranfverfe cut of the branch was covered 

 with innumerable little hemifpheres of air, 

 and many air-bubbles iffued out of the fap- 

 vefTels, which air did in part fill the tube e r y 

 as the water was drawn out of it; fo that 

 the height of the mercury could only be 

 proportionable to the excefs of the quantity 

 of water drawn off, above the quantity of 

 air which ifTued out of the wood. 



And if the quantity of air, which ifTued 

 from the wood into the tube, had been equal 

 to the quantity of water imbibed, then the 

 mercury would not rife at all ; becaufe there 

 would be no room for it in the tube. 



But if 9 parts in 12 of the water be im- 

 bibed by the branch, and in the mean time 

 but three fuch parts of air iffuelnto the tube, 

 then the mercury muft needs rife near 6 

 inches, and fo proportionably in different 

 cafes. 



I obferved in this, and moft of the follow- 

 ing experiments of this fort, that the mer- 

 cury role higheft, when the fun was very 

 clear and warm; and towards evening it 

 would fubfide 3 or 4 inches, and rife again 

 the next day as it grew warm, but feldom 

 to the fame height it did at firft. For I have 

 always found the fap-vefiels grow every day, 



after 



